Likar et al., J. Med. Chem. 14 246 (1971) prepared several hydrazones of (6-chloro-3-pyridazinyl)hydrazine. Anong these, those hydrazones produced from acetone, cyclohexanone, acetophenone and 2-butanone (with a methyl group permissibly present in the pyridazine ring) markedly reduced the titer of influenza virus A.sub.2 grown in the allantoic cavities of eggs. Activity was also shown by three compounds versus influenza A.sub.3 and two compounds were active in vivo against semliki forest virus. No compound was active against herpes or polio I in cell culture. The same group reported later in Japel et al., Il Farmaco Edizione Scientifica, 28 116 (1973) that N-oxides of some of the same hydrazones of (6-chloro-3-pyridizanyl)hydrazines were active against egg-grown influenza A.sub.2 but none were active against semliki forest virus.
The above information is also contained in Schauer et al., Proc. Int. Congress on Chemotherapy, 72 329 (1972).
In other reports of Schiff bases of 3-pyridazinylhydrazine, Steiner et al., J. Med. Chem., 24 59 (1981) report the synthesis of (6-heteroaryl-3-pyridazinyl)hydrazones, tested as hypotensive agents; Matyeus et al., Acta Chim. Acad. Sci. Hung., 106 205 (1981) report the preparation of N.sup.2 derivatives of several 2-(6-chloro-3-pyridazinyl)hydrazones--biological data are not included; and Shams et al., Ind J. Chem., 218 317 (1982) prepared Schiff bases of 6-phenyl-3-pyridazinylhydrazine using acetone, cyclohexanone, benzaldehyde, acetophenone and diphenyl ketone as the carbonyl reactants--the compounds were prepared for use in therapy or plant growth regulation.
None of the above references indicate that excellent antiviral activity would be found in hydrazones of 6-tertiary alkyl-3-pyridazinylhydrazines, nor is the synthesis of such compounds for any purpose suggested by the cited art.